Keyhole Effects in MIMO Wireless Channels - Measurements and Theory

It has been predicted theoretically that for some environments, the capacity of wireless MIMO systems can become very low even for uncorrelated signals; this effect has been termed keyhole or pinhole. In this paper the first unique measurements of this effect are presented. The measurements were performed in a controlled indoor environment that was designed to obtain a keyhole. We analyze limitations for measurement-based capacity calculations and keyhole investigations. We further present error bounds for the capacity and eigenvalue distributions due to measurement imperfections such as finite signal-to-noise ratio and multipath leakage. The bounds are compared to the measurement results and show excellent agreement. Finally, we analyze the envelope distribution and, as expected from theory, if follows a double Rayleigh. This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories, Inc.; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Research Laboratories, Inc. All rights reserved. Copyright c ©Mitsubishi Electric Research Laboratories, Inc., 2003 201 Broadway, Cambridge, Massachusetts 02139 Publication History: 1. First printing, TR-2003-136, December 2003 Keyhole Effects in MIMO Wireless Channels Measurements and Theory Peter Almers1,2, Student Member, IEEE, Fredrik Tufvesson1 and Andreas F. Molisch1,3, Senior Member, IEEE 1 Dept. of Electroscience, Lund University, Box 118, SE-221 00 Lund, Sweden. 2 TeliaSonera AB, Box 94, SE-201 20 Malmö, Sweden. 3 Mitsubishi Electric Research Labs, Cambridge, MA 02139, USA. Email: {Peter.Almers, Fredrik.Tufvesson, Andreas.Molisch}@es.lth.se Abstract—It has been predicted theoretically that for some environments, the capacity of wireless MIMO systems can become very low even for uncorrelated signals; this effect has been termed ”keyhole” or ”pinhole”. In this paper the first unique measurements of this effect are presented. The measurements were performed in a controlled indoor environment that was designed to obtain a keyhole. We analyze limitations for measurement-based capacity calculations and keyhole investigations. We further present error bounds for the capacity and eigenvalue distributions due to measurement imperfections such as finite signal-to-noise ratio and multipath leakage. The bounds are compared to the measurement results and show excellent agreement. Finally, we analyze the envelope distribution and, as expected from theory, if follows a double RayleighIt has been predicted theoretically that for some environments, the capacity of wireless MIMO systems can become very low even for uncorrelated signals; this effect has been termed ”keyhole” or ”pinhole”. In this paper the first unique measurements of this effect are presented. The measurements were performed in a controlled indoor environment that was designed to obtain a keyhole. We analyze limitations for measurement-based capacity calculations and keyhole investigations. We further present error bounds for the capacity and eigenvalue distributions due to measurement imperfections such as finite signal-to-noise ratio and multipath leakage. The bounds are compared to the measurement results and show excellent agreement. Finally, we analyze the envelope distribution and, as expected from theory, if follows a double Rayleigh